The use of 3GPP LTE systems (including LTE and LIE-Advanced systems) has increased due to an increase in both the types of user equipment (UEs) using network resources and the amount of data and bandwidth being used by various applications, such as video streaming, operating on these UEs. As a result, 3GPP LTE systems continue to develop, with the next-generation wireless communication system, 5G, aiming to answer the ever-increasing demand for bandwidth.
In particular, carrier aggregation using high-frequency bands and Multiple Input Multiple Output (MIMO) systems is being used to increase data rates. MIMO systems use multipath signal propagation to communicate with one or more UEs via multiple signals transmitted by the same evolved NodeB (eNB) on the same or overlapping frequencies that would interfere with each other if they were on the same path. This increase in uplink or downlink data may be dedicated to one UE, increasing the effective bandwidth for that UE by the number of spatial streams (Single User MIMO or SU-MIMO), or may be spread across multiple UEs using different spatial streams for each UE (Multiple User MEMO or MU-MIMO). In beamforming of MU-MEMO systems, in which multiple signals are transmitted in parallel in different directions, selection of the appropriate beam may complicate transmission and reception, especially when the high-frequency bands are used.